South Korea and Japan are backing the latest attempt by the US to negotiate an end to North Korea’s nuclear ambitions, although they insist any deal must take their concerns into account.

Han Seung-soo, prime minister of South Korea, is wary that North Korea believes it could achieve better terms by talking to Washington and keeping Seoul out of the negotiations. He described it on Monday as a “very old idea. Going over the shoulder of [South] Korea is not going to succeed.”